Filter device

ABSTRACT

The invention relates to a filter device for fluids, especially for fuels such as diesel fuel, comprising a filter housing ( 1 ) defining a longitudinal axis ( 19 ). Said filter housing comprises housing connections in the form of a fluid inlet ( 14 ) and a fluid outlet ( 24 ) and can accommodate at least one filter element ( 9 ). The fluid can, during filtering, flow through a filter medium ( 11 ) surrounding an inner filter cavity, and the filter element ( 9 ) is enclosed by an end cap ( 21 ) on its lower end facing the bottom part ( 5 ) of the filter housing ( 1 ). Said end cap comprises a passage ( 29 ) forming a fluid connection to the inner filter cavity ( 17 ) and can be fixed to an element retainer ( 23 ) of the filter housing ( 1 ). The filter device is characterized in that the element retainer ( 23 ) comprises retaining piece ( 35 ) on the bottom part ( 5 ) of the filter housing ( 1 ), said retaining piece being open towards the filter element ( 9 ) and a fluid channel ( 37 ) leading to a housing connection ( 24 ) running into it. The end cap ( 21 ) of the filter element ( 9 ) comprises a connecting piece ( 27 ) which can be accommodated in the retaining piece ( 35 ) and can be secured therein to a supporting zone. The retaining piece ( 35 ) forms an opening ( 43 ) which forms a fluid connection to the fluid channel ( 37 ) leading to the element retainer ( 23 ) and comprises a sealing arrangement ( 45, 47 ) which seals the opening from the open end of the retaining piece.

The invention relates to a filter device that is intended for fluids, in particular for fuels, such as diesel oil, and that comprises a filter housing, defining a longitudinal axis, said filter housing having housing connections in the form of a fluid inlet and a fluid outlet and can accommodate at least one filter element. During the filtration operation, the fluid can flow through a filter medium enclosing an inner filter cavity. In this case, the filter element is enclosed by an end cap on the filter element's lower end facing the bottom part of the filter housing. Said end cap comprises a passage forming a fluid connection to the inner filter cavity and can be secured on an element retainer of the filter housing. Furthermore, the invention relates to a filter element for use in such a filter device.

Filter devices of the aforementioned type are known from the prior art. Such filter devices are typically used in fuel systems for internal combustion engines in order to protect sensitive components, in particular the injection systems, against degradation due to impurities entrained in the fuel. In order to guarantee that the systems downstream of the filter will operate without any trouble over their entire service life, the filter device has to satisfy high reliability requirements. The operational reliability is greatly affected by the properties of the connection between the end cap and the element retainer. The filter element under consideration has to be accurately positioned in the filter housing by means of the element retainer. It must also be ensured that a reliable, tightly sealed fluid connection to the filter cavity is formed. In addition, it must be ensured that when it becomes necessary to change the filter element during the ongoing operations, there is a flawless connection between the end cap and the element retainer when the new filter element is installed.

Based on the above-described problem, the object of the present invention is to provide a filter device that is especially suited to meet the requirements under consideration with respect to the operating behavior.

The present invention achieves this object with a filter device having the features specified in claim 1 in its entirety.

According to the characterizing part of claim 1, the element retainer has, according to the invention, a retaining piece that is located on the bottom part of the filter housing and is open in the direction of the filter element; and a fluid channel leading to a housing connection empties into said retaining piece, with the end cap of the filter element having a connecting piece, which can be accommodated in the retaining piece and can be secured therein over a support zone having an axial length. In addition, the retaining piece has an opening, which forms a fluid connection to the fluid channel emptying into the element retainer, and has a seal arrangement, which seals off the opening from the open end of the retaining piece. Since the filter element is secured in the element retainer by way of the connecting piece of the end cap over a support zone that extends over an axial longitudinal area, it is, first of all, guaranteed that the filter element is perfectly positioned and secured in its place in the filter housing. Secondly, the connecting piece forms a fluid duct in interaction with the retaining piece of the element retainer by way of the opening in the connecting piece; and this fluid duct connects the inner filter cavity to the assigned housing connection, so that a reliably sealed fluid path is formed by means of the seal arrangement to be found at the connecting piece. Therefore, when the connecting piece is inserted into the retaining piece of the element retainer, the result is a reliable coupling between the end cap of the filter element and the element retainer during replacement operations of the filter element.

Preferably, the axial length of the support zone is not less than one-fourth of the diameter of the retaining piece.

The coupling between the end cap and the element retainer is designed to be very easy and reliable, if, according to an advantageous exemplary embodiment, the interior of the retaining piece has an insertion chamfer that diverges in the direction of the open end.

In especially advantageous exemplary embodiments, the seal arrangement is formed by sealing elements, which are arranged on the exterior of the connecting piece at an axial distance from each other that defines the length of the support zone; and these sealing elements secure the connecting piece in the element retainer by resting against the interior of the retaining piece of said element retainer.

It is of particular advantage that the connecting piece of the end cap can have a closed bottom on its end that is to be accommodated in the element retainer. In this case, the opening leading to the fluid channel is located in the wall of the connecting piece above this bottom. As a result, the connecting piece forms with its closed lower end a collecting space between the bottom and the opening located in the wall. Furthermore, any residual fluid, which may have dripped out of the inner filter cavity when the filter element was removed, remains in this collecting space, so that the risk of polluting the environment during removal of a filter element is reduced.

In especially preferred exemplary embodiments, the retaining piece of the element retainer is also closed on its lower end by a bottom that forms a depression as the lowest point of the filter housing. As a result, a collecting space for the residual fluid, which drips off during the changing of the filter, or for any dirt particles that may fall off is formed in the bottom part of the filter housing. In this case, these substances remain collected at the lowest point of the housing, that is, below the fluid channel that leads from the element retainer to the associated housing connection.

Preferably, during the filtration operation, the fluid can flow through the filter medium of the filter element from its outer unfiltered side to the inner filter cavity forming the clean side, so that the fluid channel, which empties into the retaining piece of the element retainer, leads to the housing connection that serves as the fluid outlet.

The subject matter of the invention is also a filter element for use in a filter device according to one of claims 1 to 7, with the filter element having the features specified in claim 8.

The invention is explained in detail below by means of one exemplary embodiment depicted in the drawings. Referring to the drawings:

FIG. 1 is a longitudinal sectional view of the exemplary embodiment of the inventive filter device to be described herein; and

FIG. 2 is an enlarged perspective oblique view of just the subregion drawn (cut in the longitudinal direction) of the exemplary embodiment that is adjacent to the element retainer of the filter housing.

The device has a filter housing 1 comprising a main part 3 in the form of a hollow cylinder and a closed bottom part 5 that is connected to the underside of the main part. At the upper end, a housing cover 7 is screwed to the main part 3; and this housing cover can be removed for the purpose of installing and removing a filter element 9. In the exemplary embodiment to be described herein, the filter element 9 can be traversed by flow from the outside to the inside. Therefore, the intermediate space that is located between the exterior of the filter element 9, accommodated in the housing 1, and the inner wall of the housing 1 forms the unfiltered side 13 during the filtration operation. A housing connection, which leads in the direction of the unfiltered side 13 and which forms the fluid inlet, is designated as 14 in FIG. 1. The filter medium 11 of the filter element 9 is formed by a filter mat, formed into a hollow cylinder. This filter mat surrounds a fluid-permeable support tube 15, which forms an inner filter cavity 17 that forms the clean side 16, in which the cleaned fluid may be found, during the filtration operation.

The respective end of the filter element is provided in the conventional manner with end caps 19 and 21, which form enclosures for the filter medium 11 and the support tube 15. The lower end cap 21, by means of which the filter element 9, located in the functional position in the housing 1, can be secured in the housing 1, forms both the anchoring element by means of which the filter element 9 can be anchored in an element retainer 23 on the bottom part 5 of the filter housing 1, and also a fluid-conducting device for forming a fluid connection between the inner filter cavity 17 and the housing connection 24 forming the fluid outlet in the present example. For this purpose, the end cap 21 has a connecting piece 27, which forms a passage 29 in the direction of the inner filter cavity 17. The connecting piece 27 extends from the end cap bottom 31, which forms a flat support face for the lower edge of the filter medium 11, both axially upward with a tube section 25 into the filter cavity 17 and also extends axially downward away from the end cap bottom 31, with the axial length of this part being larger than the diameter of the tube section 25. The interior of the support tube 15 rests against the exterior of the tube section 25 of the connecting piece 27 that projects into the filter cavity 17. The end cap 21 forms, with the outer circumferential edge 33 of the end cap bottom 31, the outer enclosure of the filter medium 11.

The element retainer 23 has a retaining piece 35 on the bottom part 5 of the filter housing 1; and this retaining piece is open on the upper end facing the filter element 9 and accommodates the connecting piece 27 of the filter element 9 located in the functional position. The lower end of the retaining piece 35 is closed by a bottom part 49. Above the bottom part 49, a fluid channel 37, which leads to the fluid outlet 24 and which extends transversely to the longitudinal axis 19 of the filter housing 1, empties into the retaining piece 35 of the element retainer 23. The interior of the retaining piece 35 of the element retainer 23 forms an insert chamfer 39, which diverges in the direction of the open end of the retaining piece 35 and facilitates the insertion of the connecting piece 27 into the element retainer 23. The part of the connecting piece 27 of the end cap 21 that is to be accommodated in the retaining piece 35 is stepped in the outside diameter in such a way that a fluid space 41, into which the fluid channel 37 empties, is formed between the retaining piece 35 and the connecting piece 27.

In the illustrated example, the axial length of the part of the connecting piece 27 that can be accommodated in the retaining piece 35 is equal to approximately half the size of the diameter of the opening of the retaining piece 35. The wall of the retaining piece 27 has an opening 43, which connects the interior of the connecting piece 27 and, with it, by way of the passage 29, the filter cavity 17 to the fluid outlet 24 by way of the fluid channel 37. As a result, a fluid duct is formed by means of the connecting piece 27 of the end cap 21 from the clean side 16, located in the filter cavity 17, to the fluid outlet 24. The fluid space 41 is sealed off by means of seals 45 and 47 in the direction of the interior of the retaining piece 35 of the element retainer 23. These seals are located on the exterior of the connecting piece 27 at an axial distance, so that a support zone is formed proportionate to a large axial length for the purpose of supporting the connecting piece 27 in the retaining piece 35.

In the illustrated example, the axial length of this support zone is equal to about one-half of the diameter of the opening of the retaining piece 35. Since this support extends over an axial region and has a length that can also be smaller or larger than one-half of the opening diameter of the retaining piece 35, a secure fit of the filter element 9 in the element retainer 23 is guaranteed. Owing to the seals 45, 47, a seal is formed simultaneously between the clean side 16, to which the sealed fluid space 41 also belongs, and above it the opposite unfiltered side 13, which is located in the main part 3 of the housing 1. At the same time, the sealing ring 45 is provided with a larger diameter than the sealing ring 47; and the wall 39 (insert chamfer), which tapers off downward in the form of a cone when seen in the direction of FIG. 2, extends, when viewed in the installed state of the filter element, between the two seals 45 and 47, which are, in this case, in contact with the cylindrical wall sections, which are connected at the top and the bottom to the insert chamfer 39. Owing to this arrangement, there is no need for an otherwise conventional seal between the outer circumferential edge 33 of the end cap 21 and the inner wall of the housing, so that it is possible to dispense with a seal arrangement having a correspondingly large diameter. Instead, it is possible to use sealing elements of smaller diameter in the form of O-rings as the seals 45 and 47 at the connecting piece 27, as a result of which less physical effort is required for installation and the costs are lower while at the same time the operational reliability is improved.

In the example that is depicted here, the lower end of the retaining piece 35 of the element retainer 23 forms with the closed bottom part 49 the lowest point at the bottom part 5 of the filter housing 1. When the filter element 9 that is to be changed is removed, the resulting closed bottom depression of the housing 1 forms a receiving space for any residual fluid that may have dripped off or for any dirt particles that may have fallen off. Therefore, these substances stay in a “safe zone” below the fluid channel 37 leading to the fluid outlet 24. The connecting piece 27 of the end cap 21 is also closed on the lower end, lying opposite the filter cavity 17, by means of a bottom part 51. As is evident from the figures, the opening 43, which continues the fluid path over the fluid channel 37 to the fluid outlet 24, is located in the wall of the connecting piece 27 above this bottom part 51, so that a receiving space is also formed inside the connecting piece 27. In this case, the residual fluid, which under some circumstances may drip out of the inner filter cavity 17 when the filter element 9 is removed, stays inside this space formed at the end cap 21, so that when the filter element 9 is taken out, no residual fluid can drip off the lower end, in so far as it is closed, of the filter element 9 and pollute the environment. Counter to the described direction of flow, the filter device can also be operated, if necessary, with minor structural alteration measures, in the opposite direction of flow. 

1. A filter device that is intended for fluids, in particular for fuels, such as diesel oil, and that comprises a filter housing (1), defining a longitudinal axis (19); and said filter housing has housing connections in the form of a fluid inlet (14) and a fluid outlet (24) and can accommodate at least one filter element (9); and during the filtration operation, the fluid can flow through a filter medium (11) surrounding an inner filter cavity; wherein the filter element (9) is enclosed by an end cap (21) on the filter element's lower end facing the bottom part (5) of the filter housing (1); and said end cap comprises a passage (29) forming a fluid connection to the inner filter cavity (17) and can be secured on an element retainer (23) of the filter housing (1), characterized in that the element retainer (23) has a retaining piece (35) that is located on the bottom part (5) of the filter housing (1) and that is open in the direction of the filter element (9); and a fluid channel (37) leading to a housing connection (24) empties into said retaining piece; and that the end cap (21) of the filter element (9) has a connecting piece (27), which can be accommodated in the retaining piece (35) and can be secured therein in a support zone; and that the retaining piece (35) has an opening (43), which forms a fluid connection to the fluid channel (37) emptying into the element retainer (23), and has a seal arrangement (45, 47), which seals off the opening (43) from the open end of the retaining piece (35).
 2. The filter device according to claim 1, characterized in that the axial length of the support zone is equal to at least one-fourth of the diameter of the opening of the retaining piece (35).
 3. The filter device according to claim 1, characterized in that the interior of the retaining piece (35) has an insertion chamfer (39) that diverges in the direction of the open end.
 4. The filter device according to claim 1, characterized in that the seal arrangement is formed by sealing elements (45, 47), which are arranged on the exterior of the connecting piece (27) at an axial distance from each other that corresponds to the length of the support zone; and these sealing elements secure the connecting piece (27) in the element retainer by resting against the interior of the retaining piece (35) of said element retainer (23).
 5. The filter device according to claim 1, characterized in that the connecting piece (35) of the end cap (21) has a closed bottom (51) on its end that is to be accommodated in the element retainer (23); and that the opening (43) leading to the fluid channel (37) is located in the wall of the connecting piece (27) above this bottom (51).
 6. The filter device according to claim 1, characterized in that the retaining piece (35) of the element retainer (23) is closed on its lower end by a bottom (51) that forms a depression as the lowest point of the filter housing (1).
 7. The filter device according to claim 1, characterized in that during the filtration operation, the fluid can flow through the filter medium (11) of the filter element (9) from its outer unfiltered side (13) to the inner filter cavity (17) forming the clean side (16), and that the fluid channel (37), which empties into the retaining piece (35) of the element retainer (23), leads to the housing connection that serves as the fluid outlet (24).
 8. A filter element for use in a filter device according to claim 1, said filter element comprising a filter medium (11), which surrounds an inner filter cavity (17) and which can be traversed by the respective fluid that is to be filtered for a filtration operation; wherein at least one end has an end cap (21), which encloses the filter medium (11) and which forms a passage (29) to the inner fluid cavity (17) and can be accommodated at an element retainer (23) of an associated filter housing (1), characterized in that the end cap (21) has a connecting piece (27), which forms a passage (29) to the inner filter cavity (17), can be accommodated in a retaining piece (35) of the element retainer (23), has an opening (43) for forming a fluid connection to a fluid channel (37), emptying into the element retainer (23), and has a seal arrangement (45, 47), which seals off the opening (43) from the open end of the retaining piece (35). 